A touch panel including a piezoelectric material has been proposed. When the piezoelectric material is pressed, the material generates a voltage in accordance with a temporal change of distortion occurring at the time the material was pressed. Patent Literature 1 discloses a technique that enables, using the properties, the detection of not only the touch position but also the pressing force (i.e., intensity of pressure) exerted on a touch panel including a piezoelectric material. Additionally, the use of a pyroelectric material as a piezoelectric material can enhance the sensitivity for detection of the pressing force because of its relatively high piezoelectric constant.
Patent Literature 2 discloses, as a piezoelectric film, a polarized vinylidene fluoride/tetrafluoroethylene copolymer film for touch panels or touch pressure detection.